12.8.2.2 Defragmentation Channel Retention Time

Messages are retained in the defragment channel queue only for a limited
time. When one half of the time before the first nondelivery notice is sent
has elapsed, the various parts of a message will be sent on without being
reassembled. This choice of time value eliminates the possibility of a nondelivery
notification being sent about a message in the defragment channel queue.

The notices channel keyword controls the amount of
time that can elapse before nondelivery notifications are sent, and hence
also controls the amount of time messages are retained before being sent on
in pieces. Set the notices keyword value to twice the amount
of time you wish to retain messages for possible defragmentation. For example,
a notices value of 4 would cause retention of message fragments
for two days: